U.S. patent application number 13/516590 was filed with the patent office on 2013-05-09 for programmable printed electric code, method of manufacturing the same and a programming device.
This patent application is currently assigned to TEKNOLOGIAN TUTKIMUSKESKUS VTT. The applicant listed for this patent is Ari Alastalo, Mark Allen, Mikko Aronniemi, Jaakko Leppaniemi, Tomi Mattila, Heikki Seppa. Invention is credited to Ari Alastalo, Mark Allen, Mikko Aronniemi, Jaakko Leppaniemi, Tomi Mattila, Heikki Seppa.
Application Number | 20130112755 13/516590 |
Document ID | / |
Family ID | 41462802 |
Filed Date | 2013-05-09 |
United States Patent
Application |
20130112755 |
Kind Code |
A1 |
Allen; Mark ; et
al. |
May 9, 2013 |
PROGRAMMABLE PRINTED ELECTRIC CODE, METHOD OF MANUFACTURING THE
SAME AND A PROGRAMMING DEVICE
Abstract
The present publication discloses an electronic code, comprising
a substrate (105, 10) of essentially electrically non-conducting
material,several electrically conducting code elements (108) formed
on the substrate. In accordance with the invention at least one
code element (101, 108) comprises an editable area (109), the
conductance of which can be altered electrically.
Inventors: |
Allen; Mark; (Cambridge,
GB) ; Alastalo; Ari; (Espoo, FI) ; Aronniemi;
Mikko; (Espoo, FI) ; Leppaniemi; Jaakko;
(Espoo, FI) ; Mattila; Tomi; (Espoo, FI) ;
Seppa; Heikki; (Espoo, FI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Allen; Mark
Alastalo; Ari
Aronniemi; Mikko
Leppaniemi; Jaakko
Mattila; Tomi
Seppa; Heikki |
Cambridge
Espoo
Espoo
Espoo
Espoo
Espoo |
|
GB
FI
FI
FI
FI
FI |
|
|
Assignee: |
TEKNOLOGIAN TUTKIMUSKESKUS
VTT
Espoo
FI
|
Family ID: |
41462802 |
Appl. No.: |
13/516590 |
Filed: |
December 13, 2010 |
PCT Filed: |
December 13, 2010 |
PCT NO: |
PCT/FI2010/051017 |
371 Date: |
September 26, 2012 |
Current U.S.
Class: |
235/492 ;
29/592.1 |
Current CPC
Class: |
G06K 19/06028 20130101;
G06K 19/067 20130101; G06K 1/12 20130101; Y10T 29/49002
20150115 |
Class at
Publication: |
235/492 ;
29/592.1 |
International
Class: |
G06K 19/067 20060101
G06K019/067; G06K 1/12 20060101 G06K001/12 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 16, 2009 |
FI |
20096341 |
Claims
1. An electronic code, comprising a substrate (105, 10), of
essentially electrically non-conducting material, several
electrically conducting code elements (108) formed on the
substrate, characterized in that the at least one code element
(101, 108) comprises an editable area (109), the conductance of
which can be altered electrically.
2. Code according to claim 1, characterized in that complete code
elements (101) are editable.
3. Code according to claim 1, characterized in that code elements
(101) include at least one editable area (109).
4. Code according to claim 1, characterized in that editable areas
(109) are between code lines (101).
5. Code according to any previous Claim, characterized in that code
elements (101) are conductive lines.
6. Code according to any previous Claim, characterized in that the
editable areas (109) are of such a material that they can be edited
from low conducting state to high conducting state.
7. Code according to any previous Claim, characterized in that the
editable areas (109) are of a silver nanoparticle ink.
8. Code according to any of the above Claims, characterized in that
in the measuring situation, the real component (8) of the
measurement result is reset on the surface of the uncoded material
(8) and the electronics' (1) triggering level starting the
measurement is set beforehand on the basis of the reset real
component (8).
9. Code according to any of the above Claims, characterized in
that, in the measuring situation, an algorithm seeks a suitable
triggering level starting the measurement, on the basis of the
strength of the signal.
10. A method for forming a electrically readable code,
characterized in that identical code performs (200) are
manufactured by a first party, and the performs (200) are edited to
unique codes (108) electrically by a second party.
11. A method according to claim 10, characterized in that the
performs (200) are edited by sintering.
12. A method according to any previous method claim, characterized
in that the performs (200) are edited only partially from selected
parts (109).
13. A method according to any previous method claim, characterized
in that the performs (200) are edited by galvanic contact.
14. A method according to claims 10-12, characterized in that the
performs (200) are edited by capacitive contact.
15. A method according to claims 10-12, characterized in that the
performs (200) are edited by RF-field.
16. Apparatus for editing an electronic code (200), characterized
in that it comprises means for applying an electric signal to the
code (200, 11) being edited,
17. Apparatus according to claim 16, characterized in that it
comprises means for applying galvanically an electric signal to the
code (200, 11) being edited.
18. Apparatus according to claim 16, characterized in that it
comprises means for applying capacitively an electric signal to the
code (200, 11) being edited.
19. Apparatus according to claim 16, characterized in that it
comprises means for applying an electric RF-signal to the code
(200, 11) being edited.
Description
[0001] The present invention relates to programmable printed
electric code according to the preamble of Claim 1.
[0002] The invention also relates to a manufacturing method for the
printed code and also to the programming device.
[0003] According to the prior art, both optically readable barcodes
and also remotely readable RFID identifiers are used in freight
traffic.
[0004] Barcodes have the advantage of a standardized technology,
but this technology requires a visible mark and also a reading
technique that takes place at least at sight distance, which
restricts the use of the application. The visible mark makes the
technology susceptible to abuse.
[0005] RFID technology has many advantages over the aforementioned
barcode technology, including remote readability and the
possibility to hide the code entirely in a product, which can be
used to prevent the counterfeiting of codes. However, the
identifiers used in the technology are clearly more expensive than
the barcode technology.
[0006] U.S. Pat. No. 5,818,019 discloses a solution, in which a
reading device is used to measure capacitively verification
resistance markings assigned a monetary value. The machine allows
the measurement to take place contactlessly at a short distance. In
the measurement, the orders of magnitude of several (for example, 8
items) resistors are determined by simultaneous measurement, in
such a way that the resistance value of each resistor should be
within specific predefined limits. The matter is thus one of using
a `digital technique` to estimate the electrical correctness of a
lottery ticket. If all the resistors are within the predefined
limits, the ticket is accepted, while even a single deviation will
cause a rejection.
[0007] There has also been electrically readable codes, which have
been read from close range, e.g. by sweeping with a reading device
over the code. These kinds of codes have been printed to their
final unique value. This technology is inflexible and very time
consuming, because each code has to be fabricated separately in
order to obtain the unique code value.
[0008] The invention is intended to eliminate the defects of the
state of the art described above and for this purpose create an
entirely new type of electric code, a method for manufacturing the
same and a programming device for the electric code.
[0009] The invention is based on forming the code from several
conductive lines, which include at least one area, which can be
altered after printing.
[0010] According to one preferred embodiment of the invention, the
alterable area is such that it can be altered by electrical
sintering.
[0011] More specifically, the code according to the invention is
characterized by what is stated in the characterizing portion of
Claim 1.
[0012] For its part, the method according to the invention is
characterized by what is stated in the characterizing portion of
Claim 10.
[0013] Further, the coding device according to the invention is
characterized by what is stated in the characterizing portion of
Claim 16.
[0014] Considerable advantages are gained with the aid of the
invention.
[0015] The invention provides an electric printed code the content
of which can be electrically written or programmed after
fabrication of the code structure. Fabrication can result in
identical code structures, which is desirable for mass production.
The unique content of the codes is written later with a dedicated
device possibly not by the same party of the supply chain that
fabricated the code. Therefore, the invention enables optimization
of both the fabrication process and the product value chain. One
preferred product example is the security codes.
[0016] One preferred application area of the invention are the
product originality, authenticity or document security codes or
markings for consumer products (medicine packages, valuable
products) and documents such as tickets. Mass printing of unique
electric product or security codes is problematic if the codes are
not the same. This is because fast mass printing methods such as
gravure printing are suited only to produce large numbers of
equivalent structures. Ink jet printing can do item-level
customization but ink jet is typically too slow in mass production.
The invention solves the problem by doing the code customization
using the electric sintering technique.
[0017] The invention provides a clear advantage in relation to a
barcode, thanks to the possibility to make it invisible. The
invisible code can be used to ascertain counterfeit products, among
other things, easily and cost-effectively.
[0018] In practice, the applications of the invention are similar
to those of RFID technology and barcode technology. The code
according to the invention can be either visible or hidden under a
non-transparent protective membrane. The code according to the
invention can be used, for example, in access-control applications,
product-data coding, authentication, and verification of the origin
of a product.
[0019] In relation to electronically readable RFID tags, the
invention, for its part, offers a considerable cost advantage,
because the code can be manufactured using a printing
technique.
[0020] Thanks to the optimization of the electrical properties of
the marking, the measuring electronics can be manufactured from
more inexpensive components.
[0021] In the following, the invention is examined with the aid of
examples and with reference to the accompanying drawings.
[0022] FIG. 1 shows as a top view one programmable code in
accordance with the invention.
[0023] FIG. 2 shows as a top view another programmable code in
accordance with the invention.
[0024] FIG. 3 shows as a schematic perspective view one embodiment
of the invention wherethe programming of the code can be done by
sweeping an AC sintering..
[0025] FIG. 4 shows as a schematic perspective view one embodiment
of the invention where printed ink layer is a continuous area the
local surface impedance of which is modified using-the AC sintering
apparatus in accordance with the invention.
[0026] FIG. 5 shows as a schematic top view one embodiment of the
invention where the code lines consist of well conducting parts of
fixed resistivity that are not affected by electrical sintering and
parts that change their resistance in sintering.
[0027] FIG. 6 shows as a schematic top view one embodiment of the
invention where the idea of In FIG. 19 can be extended as shown
here to optimize the non-written and written impedance levels.
[0028] FIG. 7a shows as a schematic top view one embodiment of the
invention where the code lines have only partly been printed using
an electrically sinterable ink.
[0029] FIG. 7b presents a practical realization of the
configuration of FIG. 7a.
[0030] FIG. 8 shows as a schematic top view one embodiment of the
invention wherethe contact to the code lines can be through contact
pads of size larger than the code lines.
[0031] FIG. 9 shows as a schematic top view one embodiment of the
invention where, the surface area of the electrically sinterable
code bits is varied.
[0032] FIG. 10 shows as a schematic view one embodiment of the
invention for a DC programmer circuit.
[0033] FIG. 11 shows as a schematic top view one embodiment of the
invention with modulation of the code lines to facilitate resonance
readout.
[0034] FIG. 12 shows as a schematic top view one embodiment of the
invention wherebit parts have different resistivities and the width
is varied such that the resistances of the bit parts are
essentially the same.
[0035] FIG. 13 shows as a schematic perspective view one embodiment
of the invention wherethe parts of the code line have offset in
vertical direction.
[0036] FIG. 14 shows as a schematic top view one embodiment of the
invention wherethe memory bit parts joining two consecutive code
lines together.
[0037] FIG. 15 shows one measuring device according to the
invention.
[0038] FIG. 16 shows one measurement object according to the
invention.
[0039] FIG. 17a shows the equivalent circuit between the electrodes
of the measuring device according to the invention, when there is
no code to be read between the electrodes.
[0040] FIG. 17b shows the equivalent circuit between the electrodes
of the measuring device according to the invention, where there is
a code to be read between the electrodes.
[0041] FIG. 18 shows graphically, from the point of view of the
measuring device according to the invention, the behaviour of the
real component and the imaginary component of a marking to be read,
as the code resistance increases.
[0042] Electric sintering is utilized to modify the impedance or
surface impedance of a deposited (printed, dispensed, spin-coated,
. . . ) material layer such as a dried layer of nanoparticle-based
printing ink. The impedance is generally a complex variable having
both real and imaginary parts. Either one or both of the impedance
parts (real or imaginary) can be utilized in the readout. However,
if the reader-surface contact is capacitive, a more reliable
reading is achieved with the real part of the impedance. In what
follows, electric code denotes this controlled impedance
structure.
[0043] The electric code can be in a form of a barcode that is
composed of lines of varying electrical resistivity. The barcode is
fabricated wholly or partly using an ink the resistivity of which
can be afterwards tuned by using the electrical sintering
technique. An example of such an ink is silver nanoparticle ink of
Advanced Nano Products corporation. The tuneable-resistivity lines
of the code can be wholly or in part fabricated using such an ink.
The programming device is such that it comes to electrical DC or AC
contact with the code structure applying electrical sintering to
all or part of the code lines.
[0044] Alternatively the printed structure can be an area coated
with the nanoparticle ink to which the code is written by sintering
parts of that surface area.
[0045] The following figures schematically illustrate specific
aspects of the present invention. The codes can be read, for
example, using a reader described later in this document. In the
figures below a perform 200 for a code is presented, which is
electrically altered to unique codes. In the figures, there are
presented codes where the non-sintered and sintered states of the
ink are used as the two conductance states of the code lines. With
electrical sintering the conductance can also be varied in finite
steps between the two extremes to enable a multi-level electrical
code. Furthermore, by using a voltage (current, power) sufficiently
higher than the sintering voltage (current, power) the conductors
can be broken (fuse-mode operation) enabling a third state of the
code line in addition to the non-sintered (low conductivity) and
sintered (high conductivity) states.
[0046] In FIG. 15 is presented a programmable bar code 101, which
is actually a perform 200 for a code before the programming stage.
The figure presents also a programming device. 103 and galvanic
code-device contacts 102. In programming, the programming device
103 applies DC or AC voltage to all or part of the code lines to
sinter those into conducting state. In other words, the
programmming device 103 may select any of the elements 101 for
changing the conductance value for corresponding element 101. The
contact 102 can be, for example a direct galvanic contacting onto
the ends of the code lines 101 that can have contact pads of
sufficient size. The contact pads can also recide apart from the
code in electrical contact with the code lines as presented in In
accordance with FIG. 22. The lines are printed wholly or in part
using an electrically sinterable ink such as a silver nanoparticle
ink (see In FIG. 19, In accordance with FIG. 20, In FIG. 21, In
accordance with FIG. 23, In FIG. 25 and FIG. 26 for code lines
printed only partly with a sinterable ink).
[0047] In FIG. 16 is presented a solution where the other end of
the code lines can be in electrical contact 104 to limit the number
of electrical contacts to the programming device.
[0048] In FIG. 17 is presented a solution, where the programming of
the code can be done by sweeping an AC sintering apparatus 106 over
the code lines 101 at contact or in close distance to the code
lines printed on top of a substrate 105.
[0049] In FIG. 18 is presented a solution where the printed ink
layer can be a continuous area 107 the local surface impedance of
which is modified using the AC sintering apparatus 106.
[0050] In FIG. 19 is presented a solution where the code lines 101
consist of well conducting parts 108 of fixed resistivity that are
not affected by electrical sintering and parts 109 that change
their resistance in sintering. This solution exploits the
capacitive coupling between the well conducting parts of the code
and the reader; sintering the interconnecting parts 109 increases
the physical surface area of the conducting structure by joining of
the conducting parts 108 together. The key benefits of the
described configuration include: (i) a low-cost conducting ink can
be used for 108 while a silver nanoparticle ink is used only for
109, (ii) the small size (length) of the bit part 109 allows
programming at low power or low voltage levels in comparison with
sintering of the entire code line.
[0051] In accordance with FIG. 20 the idea of In FIG. 19 can be
extended as shown here to optimize the non-written and written
impedance levels.
[0052] In FIG. 21a is presented another scheme to utilize code
lines that have only partly been printed using an electrically
sinterable ink 109. Here, a common electrode 104 is used and the
sinterable parts 109 are positioned between the common electrode
104 and each code line 101. Sintering parts 109 increases the
physical size of the conducting structure which affects the readout
of the capacitive reader like the reader described in connection
with FIG. 15.
[0053] In FIG. 7b is presented a practical realization of the
configuration of FIG. 7a. The code information is read using a
reader described in FIG. 15 by sweeping over the code. The code
lines 101 have been designated alphabetical letters A-F. Sweep 1
corresponds to the initial state, where the code lines A, C, E and
F are separated from the common electrode 104 by unsintered bits
109. These code lines with unsintered bits (state 1) provide a high
reader output amplitude. In sweep 2, code lines A, E and F have
been sintered (state 2). This transition is detected as a change
from high to low reader output amplitude. The third transition
state (state 3) corresponds to a burned bit 109. This is
demonstrated with code line E in sweep 3. Thus the reader output
for code line E is switched back from low to high amplitude. A
sinterable part 109 can be programmed from state 1 (unsintered)
directly to state 3 (burned open) as is demonstrated with code line
C. The reference code lines B and D remain connected to the common
electrode 104 by closed bits 130 during all sweeps.
[0054] In accordance with FIG. 22 the contact to the code lines 101
can be through contact pads 102 of size larger than the code lines
101.
[0055] In accordance with FIG. 23 the surface area of the
electrically sinterable code bits 115-117 is varied. In this
particular arrangement, the resistance of each bit is equal to the
square resistance Ro of the material layer. Consequently, an
applied voltage U is evenly divided over the bits while the current
density is larger for a bit with the smallest surface area 115.
Therefore, the code can be programmed by varying the sintering
voltage (or sintering time) so that only the smallest bit 115 is
sintered with a small voltage whereas applying a larger voltage (or
longer sintering time) will sinter e.g. bits 115 and 116. The
programmed bits can be verified during the programming procedure as
the total resistance changes from
3R.quadrature..fwdarw.2R.quadrature..fwdarw.R.quadrature..fwdarw.short.
[0056] FIG. 24 presents a schematic description one possible
implementation of the DC programmer circuit. The control logic 114
controls the voltage source 110, current-limiting resistor 111 and
the switch 112 that addresses the different lines of the bar code
contained in 113.
[0057] In FIG. 25 is presented a solution similar to FIG. 5 but
with modulation of the code line length 101 to facilitate readout
based on resonance occurring at line-length-dependent
frequency.
[0058] FIG. 26 presents a solution as in In accordance with FIG. 23
but with the bit parts 119, 120 and 121 having different
resistivities and the width varied such that the resistances of the
bit parts 119, 120 and 121 are essentially the same.
[0059] FIG. 27 presents a solution as in In accordance with FIG. 22
but with the parts of the code line 108 having offset in lateral
direction.
[0060] FIG. 28 presents a solution where the memory bit parts 109
are joining two consecutive code lines 108 together.
[0061] In the following typical dimensions for the code elements of
the present invention:
TABLE-US-00001 typical range typical value Width of the code
elements 101: 20 .mu.m-1 mm Length or the code elements 101: 500
.mu.m-10 mm Area of the editable parts 109: 50 .mu.m .times. 50
.mu.m- 200 .mu.m .times. 1500 .mu.m Square conductivity of the
editable parts 109. non sintered: 1 k.OMEGA.-100 k.OMEGA. sintered
conductive: 50 m.OMEGA.-1 .OMEGA. Thickness of the editable area
109: 1 .mu.m
[0062] Typical materials for the editable areas are silver
nanoparticle inks such as ANP DGH-55HTG. Also other electrically
programmable materials can be used.
[0063] FIG. 15 shows a measuring device 1 applicable for reading
the above codes presented in FIGS. 1-14. In this device two live
electrodes 4 fed by an oscillator 2 activate a current, which
travels through the surface being measured and possibly a
conductive structure in it. In the arrangement according to the
figure, the middle electrode 5 is used to measure the signal. The
capacitance (CMOS or JFET) of the wiring and amplifier 6 is
generally so large, that the impedance of the reading electrode 5
represents a capacitive short circuit. If this is not the case,
current feedback can be arranged to the amplifier 6, which makes
the amplifier's input extremely low-impedance. The signal is
detected by using phase-sensitive detection 7, which is based on
mixing the signal down with alternating electricity connected in
phase with the object and the signal is phase-displaced through 90
degrees. If the measurement is not differential, the capacitive
connection between the conductors is cancelled with a counter-phase
signal, in order to balance the bridge. The circuit according to
the arrangement of the figure measures the imaginary component 9
and real component 8 of the admittance of the surface.
[0064] FIG. 16 illustrates a situation, in which conductive
(non-transparent) codes 11 are formed on top of a substrate 10. The
substrate 10 can be paper, board, plastic, or some other similar,
typically non-conductive surface. In the figure, the coding has
been made in such a way that the width of the code 11 is constant,
but the distance between the codes is modulated. Thus, in the code
there are short gaps 12 and long gaps 13 between the conductive
structures 11. In some situations, there is a thin plastic film on
top of the code 11, which reduces the capacitive connection to the
object.
[0065] If the code according to FIG. 16 is scanned with an
arrangement according to FIG. 1, the admittance will vary in
principle between two values. The electrical circuit of FIG. 17a
depicts a situation, in which the object being measured is purely
paper and in FIG. 17b correspondingly a situation, in which there
is an electrically conductive layer on top of a substrate 10.
Because the field is divided, an accurate model requires us to
depict the situation using several capacitors and a resistor. If
there are several conductive structures on the surface over which
scanning takes place, we create an admittance modulation. In this
case, when measuring at a single frequency, an impedance
measurement produces an imaginary and a real component of the
admittance of the object. In terms of measurement, the important
question is what is the fluctuation of the imaginary and real
components of the admittance, compared to a situation, in which the
code alters both the real and the imaginary component. The central
idea of the present invention is how to perform the measurement, so
that we will be able to maximize the signal-noise ratio of the
measurement.
[0066] If we assume that the noise of the electrical resistance of
the object is not substantial, in terms of the electronics an
attempt is made to maximize the current of the real or imaginary
component. This is achieved by maximizing the capacitive connection
to the object, by making wide electrodes and a wide code and by
minimizing the distance of the code from the measuring electrodes.
However, at high frequencies the noise of the object often
determines the signal-noise ratio, and not at all the noise of the
electronics. The noise often arises from the `hunting` and tilting
of the reader and the roughness of the paper (the object). Because
most bases are not conductive, the problems cause noise mainly only
in the imaginary component of the admittance. Though the surface
has losses to some extent, the noise of the real component always
remains smaller than the noise of the imaginary component. Noise
can also arise on top of the code. If the code is highly
conductive, but the ink remains `splotchy`, among others, because
of the roughness of the paper, the problem will be that, on top of
the code, both the imaginary component and the real component will
be noisy. The real component can also remain very small, because
the electrical current travels from the input electrode to the
measuring electrode only over well conducting bridges.
[0067] If we assume a simple equivalent circuit for the object, in
which the series connection of the capacitor and the resistor
depict the impedance in a situation when the reading head is on top
of the code. Outside the code, the object is almost entirely
lossless, so that it can be depicted by only a capacitor. The
current received by the electronics can be obtained by the
equation
I = U .omega. C ( r + j ) r 2 + 1 , where r = .omega. CR ( 1 )
##EQU00001##
[0068] First, it will be noted that the current can be maximized by
using the highest possible frequency and by attempting to measure
the conductive code from as close as possible--by creating a large
capacitance.
[0069] FIG. 18 shows graphically, with the aid of a curve 40, the
behaviour of the real component and the imaginary component of the
measured admittance, when the resistance increases. The figure is a
standardized presentation, in which the measurement distance is
constant, thus the capacitance has a constant magnitude. In
addition, an ellipse 43, which depicts the admittance without the
code, is drawn in the figure. It will be noted, that the modulation
of the real component maximizes when r=1 at point 44, where the
imaginary component and real component of the measured admittance
are of equal magnitude, in which case the real and imaginary
components of the measured impedance are naturally also of equal
magnitude. An imagined situation (the black ellipse 42), in which
the good-quality conductive surface is measured, is also drawn in
the figure. The circle 41 shows a situation, in which a `holely`
code is measured, in which case the variations of both the real
component and the imaginary component are very large. When using an
insulating base material, the value of the real component and its
fluctuations are small, so that it is best to select the distance
and the conductivity of the ink in such a way that r=1 and thus we
maximize the signal-noise ratio of the real component of the
admittance. When the resistance increases to infinity, the curve
approaches the ellipse 43.
[0070] The method is essentially based on separating the real
component and the imaginary component of the admittance of the
object from each other. At high frequencies, and especially when
using a square wave, there is no accurate information on the
so-called angle error. With a square wave, which contains high
harmonics, the entire concept of a real component and an imaginary
component is, in a way, wrong. According to one embodiment of the
invention, the important fact is that the following
angle-correction equations are directed to the measured real and
imaginary components
Re{Y.sub.u}=Re{Y} cos .alpha.+Im{Y} sin .alpha. and
Im{Y.sub.u}=-Re{Y} sin .alpha.+Im{Y} cos .alpha. (2)
[0071] The sub-index u relates to the angle-corrected admittance.
The correction angle is marked by .alpha.. The basic idea of the
method is that the correction angle is chosen in such a way that
the variation of the real component is minimized, when the
measuring device is scanned over the surface of the paper (plastic)
at a point at which there is no code. Calibration can be improved
by intentionally making impressions on the surface of the paper, or
by swinging the measuring point (pen) in such a way that the
distance from the surface of the paper varies. It is preferable to
make the calibration on the surface used in the embodiment. Another
alternative is to make the calibration for the angle when scanning
the code in an area, in which there is no code. When such a
codeless, lossless surface is scanned by the measuring point, in
principle only the lossless measuring component changes. This means
that the angle can be found in such a way that the change in the
real component of the admittance is minimized. If the angle is
selected in such a way that the placing of the point on the paper
does not affect the real component of the angle, the noise of the
real component too is minimized. In practice, the calibration of
the angle must be made only once, if the reading frequency is not
changed.
[0072] Whether or not a separate independent calibration must be
made for each measuring point depends on variations in the
manufacture of the electronics.
[0073] The intention of the angle correction is thus to eliminate
from the measurement signal the variation due to changes in the
properties of the paper and the position of the point and make it
depend only on the properties of the code. The background noise is
removed.
[0074] In the angle correction, the angle of rotation of the set of
co-ordinates is selected in such a way that a change in the
lossless dielectric material in the object does not appear in the
angle-corrected Re signal.
[0075] This objective is achieved by producing for the measuring
point a change only in lossless permittivity, for example, by
lowering the point onto the paper. After this, the angle-corrected
signals Re and Im are examined. The angle alpha is adjusted until a
change caused by the adjustment appears only in the Im signal, or
the minimum of the Re signal is reached. After the correction, the
Re signal is measured, in which the change will appear only at the
code.
[0076] One central idea of the method is to calibrate the pen
acting as the measuring head, in such a way that it distinguishes
the real component and the imaginary component from each other.
This can be done by adjusting the correction angle in such a way
that the pen produces no changes in the real component when it is
placed on a lossless dielectric surface. Another way is to scratch
the dielectric surface and ensure that fluctuations do not take
place in the real component when scanning over the surface. In a
practical measuring situation, the real component is reset on the
surface of the paper and the triggering level is set beforehand, or
the algorithm seeks a suitable triggering level on the basis of the
signal strength. Because the noise in the real component is small,
the triggering level can be set very close to zero. Only in a
situation, in which the conductivity of the code is dimensioned
wrongly, or the code is `splotchy`, is it worth using the
longitudinal modulation of the vector instead of the modulation of
the real component. In principle, taken generally, the code can be
detected by weighting the lengths of the real component and the
imaginary component in a suitable ratio to each other, in such a
way that the signal-noise ratio is optimized.
[0077] In principle, we can measure the correct conductivity of the
code from the real and imaginary components of the admittance. The
depiction is mathematically very difficult, because the field is
divided. The depiction depends on the mean distance of the pen, the
width of the code compared to the width of the electrodes, etc. If,
however, we calibrate the pen for a specific application, we can
experimentally (or numerically using FEM computation) seek the
representation
r=f{Re{Y},Im{Y}} (3)
in such a way that the change of the variable r on top of and
outside of the code is independent of small variations in distance.
This is simply due to the fact that both terms are proportional to
the distance, so that by using both variables we can eliminate the
changes in distance. It should be noted that the method in question
does not measure the absolute resistivity of the code, but instead
is proportion to the difference in the resistivities of the code
and the paper. Such a more accurate measurement of conductivity is
important, if we are measuring the sensor information. However, we
can return the measurement of the sensor information to the
measurement of the real component, if, in addition to measurement
lines, we place reference lines in the code, the conductivity of
which is known, or if its value is given in connection with the
code information. In this case, we can calculate the resistance
value r of the resistivity of the sensor from the equation from the
real and imaginary components of the admittance Y
r a = r ref Re a ( Y ) Re ref ( Y ) Re ref ( Y ) 2 + Im ref ( Y ) 2
Re a ( Y ) 2 + Im a ( Y ) 2 ( 4 ) ##EQU00002##
[0078] In the equation, the sub-index ref refers to the measurement
of the reference code and the sub-index a to the measurement of the
sensor. Of course, the equation can be used reliably only if the
reference has a geometry that is similar to that of the sensor. If
either the real component or the imaginary component dominates the
admittance, the equation if, of course, simplified. On the other
hand, it often happens that the imaginary component is nearly the
same on top of both the reference and the sensor, and for this
reason the rough conductivity of the sensor is often obtained by
simple mathematics. It should be noted that, in equation 4, the
admittance Y depicts the angle-corrected admittance.
[0079] The code can be made in several different ways. One
possibility is to `copy` the method used in barcodes. Here,
however, a way is introduced, which permits a natural way to
eliminate the speed variations that take place in scanning with a
pen or mouse. In addition, the way described is based on the
triggering level being set close to the impedance of the paper and
thus not using the code as a `zero reference`. In the code of FIG.
2, the information is stored in the width modulation of the lines
and the width of a conducting line is constant. If we divide the
number of samples, which accumulate during the time of the code
(non-conducting material) and we divide this with a number, which
is either the maximum of the conducting codes close to the number
of samples, or by the mean of the number of accumulated samples
from the conductive areas nearby, we will obtain standardized code
information, which depicts the distance of two lines from each
other to the width of the adjacent lines. This number is
independent of speed. On the other hand, using a known code and a
fixed triggering level, the ratio between a long code and a short
code is constant and this permits the detection or erroneous
readings. This type of coding also has the advantage that, if the
width of the line is minimized, there is more pure paper than code
in the surface being read and we can keep the code less visible.
Over a long period of time with good material we can possibly even
achieve a 40-.mu.m wide line, in which case the visibility of the
code will be further reduced. The width of a suitable short code is
of the same order as the width of a conducting area and
correspondingly a wide gap can be 1.5-3 times wider, depending on
the signal-noise rate of the reading and the selected
error-correction algorithm. If the coefficient is only 1.5, we
obtain an information density of 1/2.25 bits per unit of travel.
For example, a 40-.mu.m line would conduct 1/90 bit/.mu.m, i.e. a
96-bit EPC code would require a code about 9-mm long. In practice,
a pleasant scanning length with a pen-like point is 3 cm-5 cm, so
that an EPC code would require a code width of at least 250 Even
longer distances can be scanned with a pen and, especially if we
use a mouse-type interface, the distance can easily be 5 cm-10 cm.
This means that even large numbers of bits can be coded
electronically. In addition, if a 2D code is made from a
corresponding method, the amount of information can be many times
this.
[0080] According to one embodiment of the invention, the reading of
the code can thus be optimized as follows. Once the electrode
structure, the distance from the code, and the reading frequency
are settled, the conductivity of the ink is optimized, in such a
way that the reactance of the capacitance is of the same order as
the resistance of the conductive ink. With the aid of the measuring
electronics, the measured real and imaginary components of the
admittance are corrected by angle correction, in such a way that
the real component measures only losses. This can be seen easily by
bringing the point close to the non-conductive dielectric surface.
The correction can be analog in connection with a capacitive
bridge, or after mixing. The correction can also be made digitally,
after AD correction. After the angle correction, the interpretation
of the code is made mainly from the real component. If, for
example, due to the examination of the origin of the ink we require
better information on the conductivity, we can, with the aid of the
admittance, calculate the real component of the impedance and
decide the conductivity of the code from this.
[0081] The invention can also be described as follows. The
permittivity of the dielectric material being measured (paper,
board, plastic) is complex, containing a lossy and a lossless
component. The reader according to the invention measures both of
these. The lossless component is formed of polarization. The lossy
component is formed either of the losses relating to polarization,
or of conductivity losses. The permittivity of clean paper is
almost entirely lossless.
[0082] When moving the point of the reader, which is represented,
for example, by the electrodes 5 and 4 of FIGS. 3a and 3b, on the
surface of the object being measured (paper, board, plastic) in a
place in which there is no code, the signal proportional to the
lossless permittivity measured by the point of the reader changes
for the following reasons:
[0083] 1. Due to the fibrous nature of the paper the permittivity
varies at different points.
[0084] 2. The moisture absorbed by the paper changes the
permittivity in different ways at different places.
[0085] 3. When the point tilts, the connection from the point to
the paper changes and affects the signal.
[0086] There is no signal at all proportional to lossy
permittivity.
[0087] The signal proportional to this lossless permittivity
appears in both angle-corrected signals (Re_orig and Im_orig),
which is due to the phase difference between the modulation and
demodulation. By altering the correction angle alpha, this phase
difference can be altered (also called rotation of the
coordinates). By altering the angle, new signals Re and Im can be
formed. By means of a suitable angle the signal caused by the
variation in lossless permittivity appears only in the Im
component. At the same time, it vanishes entirely from the Re
signal.
[0088] Thus, in practice the angle correction is made by moving the
reader on clean paper and adjusting the angle alpha, until the
change caused by the movement appears only in the imaginary
component, or if changes appear in the real component, they are
minimal and very small. In that case, the real component thus
measures only the lossy, resistive component of the impedance.
[0089] Thus, because there is only the lossy permittivity at the
code, the Re signal changes only at the code.
[0090] The angle-correction operation described above is typically
one-off in nature and need only be made once, or repeated at
relatively infrequent intervals (once a month--once a year).
[0091] The invention can be implemented using voltage or current
input, in which case the voltage input is used to measure the
current between the measuring electrodes and the current input is
used to measure the voltage between the measuring electrodes. The
measuring variables (current or voltage) can be referred to more
generally as measuring signals.
[0092] In the following are presented alternative solutions in
accordance with the invention [0093] RFID: chip-id programming.
[0094] Conventional fuse operation can also be utilized for the
memory bits such that the bit is not sintered in writing but burned
broken with high-enough voltage or current. [0095] In addition to a
capacitive sweep-over readout, the readout can done using a
high-enough frequency or large-enough code structure such that a
code line resonates when the bit is sintered (length of the code
line is, for example, half a wavelength) and does not resonate when
the bit is not sintered (low-conductance or non-conducting state).
Resonance of the code line can be detected by illuminating the code
line with the specific frequency and measuring the backscattered
signal. Resolution of different code lines can be done by focusing
the illuminating field to the local area of the code line with
near-field sweep-over excitation and detection or using a scanning
narrow beam. Alternatively, the lengths of the different lines of
the code can be different as shown in In FIG. 25 to resonate at
different frequencies enabling line resolution in frequency. This
latter approach would enable far-field readout at a distance
without scanning in place. Also writing the code using the
resonance techniques is possible if high-enough voltage can be
induced over the initially non-conducting bit. Writing of the
fuse-mode bit that is initially conducting requires higher field
than sintering. A further embodiment of this approach, targeting
better resolution in frequency, is having the resonator structure,
for example, capacitively coupled to a separate resonator such as
an antenna structure. [0096] The solution of In accordance with
FIG. 23 with different sized memory bit parts resulting in
sintering at different voltages or sintering times can also be
realized using inks of different sintering temperature, voltage or
time in combination with varying the sizes of the memory bit parts
as shown in FIG. 26. [0097] The parts of the code lines coming
close from opposite directions to be joined by the memory part as
shown, for example, in hi FIG. 19, can also have a horizontal
offset and go side by side for a short distance where the memory
part is placed as shown in FIG. 27. This can relax the alignment
requirements of the two or more parts of each code line. [0098] One
further particular code structure is shown in FIG. 28. Here the
memory bit part joins consecutive code lines together. [0099]
Instead of silver nanoparticle ink also other metal nanoparticle
inks like copper nanoparticle ink may be used in connection with
the invention.
* * * * *